Turbo increases gas mileage? - Toyota Yaris Forums

fbarcenas · 01-31-2010, 10:43 PM

Someone mentioned to me that adding a turbo kit to my Yaris would increase my gass mileage; since in theory a turbo engine creates power more efficiently than a N/A engine does.

May be it's true unless adding a turbo could would temp you into using it at every stop light. Then I guess it would defeat the purpose of having it for fuel economy. right?

Yaris Hilton · 01-31-2010, 11:14 PM

You're unlikely to gain mileage by adding a turbo to an existing engine. Like you said, you'll probably use the extra horsepower and burn more fuel. The big opportunity for gaining mileage comes by using a smaller engine and turbocharging it to the same peak power as a larger normally aspirated engine. If you turbocharge one and still drive it the same way you probably won't lose any mileage, but where's the fun in adding all that extra power and not ever using it?

fbarcenas · 01-31-2010, 11:29 PM

So It wouldn't hurt to get the turbo kit(unless money is an issue), but if you needed the power one day, you've got it.

HMM.. I like tinkering , so I might just get the turbo to have something else to tinker and play with.

Yaris Hilton · 02-01-2010, 07:30 AM

Maybe.

I've got some experience hotrodding engines, and it normally takes a LOT more tinkering than you expect to make things work as you want them to. I'm not messing with my daily driver, ever again.

talnlnky · 02-01-2010, 11:55 AM

not sure if there is much in the way of turbo kits for the yaris.... I think you have to do all the grunt & brain work yourself... or pay A LOT to have a shop do it....

dean_park · 02-01-2010, 01:50 PM

I've often thought about this too. I think some eco tuning and possibly some internals (like lower compression pistons) would be needed to bump the efficiency with the turbo. I think the way people are starting to look at fuel economy and efficiency, there is likely to be a few companies that will start up and start making eco-turbo kits. If I was younger, without kids, I'd probably jump on that market now.

why? · 02-04-2010, 07:50 PM

All the eco boards seem to agree that adding a low pressure turbo will help gas mileage. I also agree on not tinkering with your daily driver if its the only car you have. That could be a nightmare.

Black Yaris · 02-04-2010, 08:13 PM

check this out for shits and giggles about fuel econ

http://www.youtube.com/watch?v=dKTOyiKLARk

advocate · 02-05-2010, 01:21 AM

Quote:

Originally Posted by Black Yaris

check this out for shits and giggles about fuel econ

http://www.youtube.com/watch?v=dKTOyiKLARk

Completely unrelated but contains plenty of good science so I'll let it slide this time.

Nexus1155 · 02-05-2010, 10:19 AM

you're adding another means of power without the sacrifice of displacement. So in terms that you would use less gas/engine load to get to obtain a certain speed and maintain that speed would be less than if you were naturally aspirated at a lesser power... do you understand what i am saying?

Yaris Hilton · 02-05-2010, 10:37 AM

Yes, but it's not necessarily correct. With a gasoline engine you have a throttle in the intake passage that consumes a great deal of power as pumping losses. The turbo draws pumping energy from what's normally wasted in the exhaust and helps to overcome that, but doesn't under all conditions. As you get to higher manifold pressures, the turbo, if oversized for steady state full throttle conditions as it usually is, has to be limited either by letting exhaust flow out bypassing the turbine through a waste gate (properly named as it wastes all that exhaust energy) or by restricting the outflow from the compressor impeller (which leaves the exhaust backpressure elevated, increases pumping loss and risks causing compressor stall.) Compressor outflow restriction is seldom used nowadays. Additionally, at higher power levels the mixture is likely to have to be richened, the ignition timing is likely to have to be retarded, and water/alcohol injection may be required to suppress detonation. All of these waste energy. Whether or not a given existing engine can deliver better mileage after installation of a turbo can only be determined by before and after testing, preferably on a dyno with a controlled driving regimen for consistency. Any gain will be small with a gasoline engine. The real benefit is when the turbo lets you swap out that big old naturally aspirated engine for a small one that normally operates with the throttle open wider for less pumping losses at partial power, and uses the turbo for those occasional bursts of higher power. Not worth it to add on a turbo unless you want it primarily for extra power. But if it's properly done, you really shouldn't lose any significant mileage either, unless you do lower the compression ratio.

Diesels are a different matter. With no throttle, they have far lower pumping losses at low power operation than gasoline engines and with a turbo assisting the pumping may have negative pumping losses, i.e., gaining a slight bit of power from the turbo pushing the pistons down. Extra air in the cylinders gets heated by combustion and expands as a passive working fluid even when no more fuel is injected. You almost get "something for nothing" with the additional air.

01-31-2010, 10:43 PM	#1
fbarcenas Drives: 2010 Toyota Yaris Hatchback Join Date: Jan 2010 Location: Jalisco, Mexico Posts: 3	Turbo increases gas mileage? Someone mentioned to me that adding a turbo kit to my Yaris would increase my gass mileage; since in theory a turbo engine creates power more efficiently than a N/A engine does. May be it's true unless adding a turbo could would temp you into using it at every stop light. Then I guess it would defeat the purpose of having it for fuel economy. right?

02-01-2010, 11:55 AM	#5
talnlnky Audio Junky Drives: 08 liftback Join Date: Oct 2008 Location: Spokane, Wa Posts: 1,412	not sure if there is much in the way of turbo kits for the yaris.... I think you have to do all the grunt & brain work yourself... or pay A LOT to have a shop do it.... __________________

02-04-2010, 07:50 PM	#7
why? Only Happy When it Rains View User's Garage Drives: Yaris LB Join Date: Jan 2006 Location: harnett county NC Posts: 4,097	All the eco boards seem to agree that adding a low pressure turbo will help gas mileage. I also agree on not tinkering with your daily driver if its the only car you have. That could be a nightmare. __________________ Colin Chapman disciple

02-04-2010, 08:13 PM	#8
Black Yaris der Zeck View User's Garage Drives: '05 Audi A4 1.8t quattro Join Date: Sep 2006 Location: Toledo, OH Posts: 5,231	check this out for shits and giggles about fuel econ http://www.youtube.com/watch?v=dKTOyiKLARk __________________

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01-31-2010, 11:14 PM	#2
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	You're unlikely to gain mileage by adding a turbo to an existing engine. Like you said, you'll probably use the extra horsepower and burn more fuel. The big opportunity for gaining mileage comes by using a smaller engine and turbocharging it to the same peak power as a larger normally aspirated engine. If you turbocharge one and still drive it the same way you probably won't lose any mileage, but where's the fun in adding all that extra power and not ever using it?

01-31-2010, 11:29 PM	#3
fbarcenas Drives: 2010 Toyota Yaris Hatchback Join Date: Jan 2010 Location: Jalisco, Mexico Posts: 3	So It wouldn't hurt to get the turbo kit(unless money is an issue), but if you needed the power one day, you've got it. HMM.. I like tinkering , so I might just get the turbo to have something else to tinker and play with.

02-01-2010, 07:30 AM	#4
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	Maybe. I've got some experience hotrodding engines, and it normally takes a LOT more tinkering than you expect to make things work as you want them to. I'm not messing with my daily driver, ever again.

02-01-2010, 01:50 PM	#6
dean_park Drives: 2011 VW Golf TDI Join Date: Oct 2009 Location: Wentzville, MO Posts: 191	I've often thought about this too. I think some eco tuning and possibly some internals (like lower compression pistons) would be needed to bump the efficiency with the turbo. I think the way people are starting to look at fuel economy and efficiency, there is likely to be a few companies that will start up and start making eco-turbo kits. If I was younger, without kids, I'd probably jump on that market now.

02-05-2010, 10:19 AM	#10
Nexus1155 Bathroom + Laptop = <3 Drives: Audi Join Date: Aug 2006 Location: Dorchester Posts: 1,009	you're adding another means of power without the sacrifice of displacement. So in terms that you would use less gas/engine load to get to obtain a certain speed and maintain that speed would be less than if you were naturally aspirated at a lesser power... do you understand what i am saying?

02-05-2010, 10:37 AM	#11
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	Yes, but it's not necessarily correct. With a gasoline engine you have a throttle in the intake passage that consumes a great deal of power as pumping losses. The turbo draws pumping energy from what's normally wasted in the exhaust and helps to overcome that, but doesn't under all conditions. As you get to higher manifold pressures, the turbo, if oversized for steady state full throttle conditions as it usually is, has to be limited either by letting exhaust flow out bypassing the turbine through a waste gate (properly named as it wastes all that exhaust energy) or by restricting the outflow from the compressor impeller (which leaves the exhaust backpressure elevated, increases pumping loss and risks causing compressor stall.) Compressor outflow restriction is seldom used nowadays. Additionally, at higher power levels the mixture is likely to have to be richened, the ignition timing is likely to have to be retarded, and water/alcohol injection may be required to suppress detonation. All of these waste energy. Whether or not a given existing engine can deliver better mileage after installation of a turbo can only be determined by before and after testing, preferably on a dyno with a controlled driving regimen for consistency. Any gain will be small with a gasoline engine. The real benefit is when the turbo lets you swap out that big old naturally aspirated engine for a small one that normally operates with the throttle open wider for less pumping losses at partial power, and uses the turbo for those occasional bursts of higher power. Not worth it to add on a turbo unless you want it primarily for extra power. But if it's properly done, you really shouldn't lose any significant mileage either, unless you do lower the compression ratio. Diesels are a different matter. With no throttle, they have far lower pumping losses at low power operation than gasoline engines and with a turbo assisting the pumping may have negative pumping losses, i.e., gaining a slight bit of power from the turbo pushing the pistons down. Extra air in the cylinders gets heated by combustion and expands as a passive working fluid even when no more fuel is injected. You almost get "something for nothing" with the additional air.